150 



The Canadian Field-Naturalist 



[Vol. XXXIV. 



Fig. 2. Argulus piperatus: first and second 

 antennae of male, mucli enlarged. 



Lateral claw of basal joint of first antenna long 

 and slender and curved into a half circle; anterior 

 claw shcrt and weak. Second joint slender, three 

 times the length of the terminal joint, and armed at 

 the distal anterior corner with a short spine ; ter- 

 minal joint tipped with two spines. Second anten- 

 na of the usual pattern, the basal joint one-half 

 wider than the succeeding joints and tipped with a 

 long spine; second joint with two spmes, third and 

 fourth joints with one spine each. 



Fig. 



Argulus piperatus: supporting rods in 

 sucking disks: much enlarged. 



Sucking disks of second maxillae far forward 

 and well separated, each about 15'; of the width 

 of the carapace; the supporting rods slender and 

 far apart, each made up of four cylindrical joints 

 which diminish regularly in size from the base out- 

 wardly, and which do not quite reach the margin. 

 The latter has a fringe of flattened fleshy setae, at- 

 tached side by side in a single row. 



Fig. 4. Argulus piperatus: maxillijied of male: 

 much enlarged. 



The maxillipeds are rather short but stout ; the 



triangular plate on their base is wide posteriorly 



and much narrowed anteriorly, but extends to the 



anterior margin of the appendage; the teeth are 



long and wide and bluntly rounded. Inside of the 



base of the appendage, on the ventral surface of 



the head, is an accessory tooth of the same pattern 



as those on the plate itself. 



The rami of the swimming legs reach consider- 

 ably beyond the margin of the carapace. The 

 lobes en the basal joints of the fourth legs are 

 small and not very prominent. 



Color a light cartilage gray, the dorsal surface 

 covered with small black dots, as though it had 

 been sprinkled with pepper. These dots are not 

 evenly distributed but are massed as shown in the 

 figure. 



, Total length 5 mm. Carapace 4 mm. long, 3.25 

 mm. wide. Abdomen 1 mm. long, 0.90 mm. wide. 



Fig. 'i. Dorsal view of Argulus piperatus. male. 

 The line represents a length of 1 mm. 



Specific characters of male. Carapace relative- 

 ly the same size and shape as in the female; abdo- 

 men longer, one-third the length of the carapace, 

 the longitudinal and transverse diameters in the 

 proportion of 15 to 11. Anal sinus not as deep, 

 only 14' , of the length of the abdomen and never 

 closed by the approximation of the posterior lobes. 



Fig. 6. Argulus, piiieratus: third legs of male, much 

 enlarged. 



Of the accessory sexual characters the peg on 



the anterior margin of the basal joint of the fourth 



legs is a broad cone, inclined strongly outwards and 



bluntly rounded at the tip, with a tiny spine on its 



